The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government for Government purposes without the payment of any royalties thereon or therefor.
The present invention relates to temperature sensors and in particular to high temperature optical temperature sensors.
Selective emitters are devices for converting thermal energy into narrow band radiation or energy. Most solid state materials have nearly a constant spectral emittance (gray body). The spectral emittance of a rare earth is characterized by several emission bands in the visible and near infrared region resulting from electronic transitions from the lowest excited states. Materials containing rare earths (e.g., ytterbium (Yb), erbium (Er), thulium (Tm), dysprosium (DY), and holmium (Ho)) can emit in narrow wavelength bands in the visible and near infrared region of the spectrum.
Selective emitters have been used in thermophotovoltaic energy conversion systems such as those described in U.S. Pat. Nos. 4,584,426 and 5,080,724.
Many existing temperature sensors are unsuitable and/or uneconomical for use in high temperature (greater than 2,000xc2x0 K) harsh environments. For example, metal thermocouples suffer from high thermal conductivity (e.g., 1 W/cmK) that conducts heat away from the measurement site, causing errors in the measurement. Other sensors may require sophisticated electronics or other techniques to eliminate errors from the measurements.
An optical temperature sensor includes an emitter having a selective energy emission band. The emitter emits energy within the emission band in response to the emitter temperature. The sensor also includes a light pipe having a first and a second end. The first end communicates with the emitter. Also included is an optical bandpass filter communicating with the second end. The filter has a pass band corresponding to the emission band. Also included is a detector communicating with the filter. The detector detects the emitted energy as a measure of the temperature.